Read and parse a Json File in C#

Question

I have spent the best part of two days "faffing" about with code samples and etc., trying to read a very large JSON file into an array in c# so I can later split it up into a 2d array for processing.

The problem I was having was I could not find any examples of people doing what I was trying to do. This meant I was just editing code a little an hoping for the best.

I have managed to get something working that will:

• Read the file Miss out headers and only read values into array.
• Place a certain amount of values on each line of an array. (So I could later split it an put into 2d array)

This was done with the code below but it crashes the program after entering a few lines into the array. This might have to do with the file size.

// If the file extension was a jave file the following 
// load method will be use else it will move on to the 
// next else if statement
if (fileExtension == ".json") 
{
    int count = 0;
    int count2 = 0;
    int inOrOut = 0;
    int nRecords=1; 
    JsonTextReader reader = new JsonTextReader(new StreamReader(txtLoaction.Text));
    string[] rawData = new string[5];
    while (reader.Read())
    {
        if (reader.Value != null)
            if (inOrOut == 1)
            {
                if (count == 6)
                {
                    nRecords++;
                    Array.Resize(ref rawData, nRecords);
                    //textBox1.Text += "\r\n";
                    count = 0;
                }
                rawData[count2] += reader.Value + ","; //+"\r\n"
                inOrOut = 0;
                count++;
                if (count2 == 500)
                {
                    MessageBox.Show(rawData[499]);
                }
            }
            else
            {
                inOrOut = 1;
            }
    } 
}

A snippet of the JSON I am working with is:

[ 
    { "millis": "1000", 
      "stamp": "1273010254", 
      "datetime": "2010/5/4 21:57:34", 
      "light": "333", 
      "temp": "78.32", 
      "vcc": "3.54" }, 
] 

I need the values out of this JSON. For example, I need "3.54", but I would not want it to print the "vcc".

I am hoping someone can show me how to read a JSON file in and only extract the data that I need and put it into an array or something that I can use to later put into an array.

Answer 1

How about making all the things easier?

public void LoadJson()
{
    using (StreamReader r = new StreamReader("file.json"))
    {
        string json = r.ReadToEnd();
        List<Item> items = JsonConvert.DeserializeObject<List<Item>>(json);
    }
}

public class Item
{
    public int millis;
    public string stamp;
    public DateTime datetime;
    public string light;
    public float temp;
    public float vcc;
}

You can even get the values dynamically without declaring Item class.

dynamic array = JsonConvert.DeserializeObject(json);
foreach(var item in array)
{
    Console.WriteLine("{0} {1}", item.temp, item.vcc);
}

Answer 2

For finding the right path I'm using

   var pathToJson = Path.Combine("my","path","config","default.Business.Area.json");
   var r = new StreamReader(pathToJson);
   var myJson = r.ReadToEnd();

   // my/path/config/default.Business.Area.json 
   [...] do parsing here 

Path.Combine uses the Path.PathSeparator and it checks whether the first path has already a separator at the end so it will not duplicate the separators. Additionally, it checks whether the path elements to combine have invalid chars.

See https://stackoverflow.com/a/32071002/4420355

Answer 3

Doing this yourself is an awful idea. Use Json.NET. It has already solved the problem better than most programmers could if they were given months on end to work on it. As for your specific needs, parsing into arrays and such, check the documentation, particularly on JsonTextReader. Basically, Json.NET handles JSON arrays natively and will parse them into strings, ints, or whatever the type happens to be without prompting from you. Here is a direct link to the basic code usages for both the reader and the writer, so you can have that open in a spare window while you're learning to work with this.

This is for the best: Be lazy this time and use a library so you solve this common problem forever.

Answer 4

Based on @L.B.'s solution, the (typed as Object rather than Anonymous) VB code is

Dim oJson as Object = JsonConvert.DeserializeObject(File.ReadAllText(MyFilePath))

I should mention that this is quick and useful for constructing HTTP call content where the type isn't required. And using Object rather than Anonymous means you can maintain Option Strict On in your Visual Studio environment - I hate turning that off.